The automotive industry has turned to the use of interior trim components, such as door panels, comprising a polyvinyl chloride shell. See, for example, the trim components disclosed in U.S. Pat. No. 3,123,403. The acceptance of such components has been because inter alia this type of construction permits a wide latitude in styling and color, and grain effects which are most desirable, particularly in the interior design of automobiles.
The current state of the art includes a preformed grain vinyl shell made from dried thermoplastic powder particles which are applied to a heated shell mold from a powder box to form a continuous one-piece shell.
In order to enhance the interior decor of an automobile, interior door panels and other parts have been prepared which include two separate plastic shell sections joined by a mechanical fastener.
U.S. Pat. No. 4,562,025 issued Dec. 31, 1985, with a common assignee to this present invention, covers a mold method and apparatus for multi-color plastic shells which shell segments have their edges bonded at a particular break-line.
U.S. Pat. No. 4,610,620, issued Sep. 9, 1986, discloses an apparatus for loading and releasing a recharge of two or more colors of thermoplastic color from separate compartments in a charge box for gravity flow into a mold configured to produce two shell segments and a separate overlapping color connector to bond the shell segments to form a one piece shell with two or more color tones to enhance the color of the interior of an automobile. An open-ended charge box is provided with a divider wall to form two separate compartments, each filled with a predetermined quantity of different powder. The mold has a division surface which cooperates with the divider wall to separate the powder content in each compartment of the charge box. The charge box releases the powder from the separate charge box compartments to flow evenly across the open end of the mold by gravity. A fixed gasket seals the division surface and the divider wall so as to produce separate two-tone segments on the heated surfaces of the mold. In theory, the seal gasket keeps the division surface clean for a subsequent application of the material thereagainst to form a connector that bonds the previously cast two-tone segments to form a single piece article with an integral joint between the two-tone segments. In practice, such a fixed gasket must conform to a division surface on each of a number of heated molds. The molds can be heated by suitable means such as hot air units of the type shown in U.S. Pat. No. 4,623,503 dated Nov. 18, 1986. Tolerance differences in the mold dimensions may leave margin gaps between the fixed gasket and the division surface. Powder from the charge box can seep into such gaps onto the division surface to create color smudges in the finish bond connector.
A further assembly utilized by the assignee of the subject invention includes an inflatable seal gasket which is operative to selectively bridge between the divider wall and the division surface when a charge box and heated mold are connected together. The inflatable seal includes a sealing bead thereon configured to completely cover the division surface to prevent seepage of the powder material from the casting surfaces to the division surface and to prevent resulting color smudges in a subsequently formed connector bond. The assembly solves the prior art problem of seepage onto the division surface due to geometric shape by inflating the gasket. However, a problem with this type of seal gasket is that the gasket is slidable along the divider wall and is allowed to slide therealong at any time preceding and during the casting operation. The seal gasket may drift and slide out of longitudinal alignment with the division surface and divider wall over a period of time causing leakage or other failures of the gasket and scrap shells.
In U.S. Pat. No. 5,074,773 which is incorporated herein by reference and commonly assigned with this application, an assembly is provided for molding a two-tone, thin-walled plastic shell in a heated open-ended mold from a charge of thermoplastic powder material in an open-ended charge box. The assembly includes a heated open-ended mold having a rib extending therefrom establishing two separate casting surfaces thereabout, a charge box adapted to be connected to the heated open-ended mold in open-ended relationship to form a closed system for casting the powder material and having a divider wall establishing two sources of the powder material. Also included is a seal gasket means longitudinally slidable along the divider wall for selectively bridging between the divider wall and the rib when the heated open-ended mold and the charge box are connected in the closed system. The assembly is characterized by including retaining means selectively secured to said divider wall for receiving and maintaining the sealed gasket means at a predetermined position longitudinally along the divider wall. The seal gasket is held longitudinally to prevent damage thereto during manufacturing of the thin-walled hollow shells and also to prevent damage to shells formed with respect to the gasket.
One problem with each of the aforesaid casting assemblies is that the divider wall is a one piece member for retaining the sealing gasket with respect to the divider rib or division surface on the heated mold. In certain applications the divider wall is a cast or machined aluminum part. In other applications the divider wall is a fiberglass reinforced epoxy panel having a cast seal retainer member directly fixed to the end of the panel by suitable fasteners such as bolts. The only lateral adjustment of the divider wall to compensate for dimensional variations between the sealing gasket and the divider rib is to reposition the entire divider wall or to bend it with respect to the walls of the charge box so as to relocate the sealing gasket into better alignment with the divider rib or division surface when the charge box and heated open ended mold are joined together in an open-ended relationship. Such adjustment will not provide the desired accuracy required in most assemblies for casting accurately formed two color shells with a precision joint formed therebetween.